Poor bondability of bonding pads is a continuing issue to low-k intermetal dielectric (IMD) layers. Pad peeling and craters have been found during wire bonding processes and post-testing. Mechanical stress also degrades performance.
For example, FIG. 1 illustrates a conventional N level bonding pad 10 with metal via anchors 12 (through IMD layer 11) anchoring and electrically connecting N level bonding pad 10 to N-1 level metal layer 14. Bonding wire 20 is electrically affixed to N level bonding pad 10 as at 22.
Metal via plugs 16 (through IMD layer 15) electrically connect N-1 level metal layer 14 to N-2 level metal layer 18. FIG. 2 is a cross-section of FIG. 1 taken along line 2—2 of FIG. 1, illustrating that the N-1 level, etc., metal layer 14 is a solid sheet layer. This structure suffers from the above described shortfalls.
U.S. Pat. No. 6,258,715 B1 to Yu et al. describes plugs under bonding pads to improve adhesion.
U.S. Pat. No. 6,236,114 B1 to Huang et al. describes a bonding pad with extra vias.
U.S. Pat. No. 5,923,088 to Shiue et al. describes a bonding pad structure with via plugs thereunder.
U.S. Pat. No. 5,739,587 to Sato describes another bonding pad structure with via plugs thereunder.